MH
M.H. Helsdingen
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A new semi-analytical model is developed to predict the dynamic response of slender gates in combination with an overhang, which are subjected to standing waves. Still little is known for these types of gates for this specific forcing type. The semi-analytical model is still in its development phase and must be validated on its performance. This thesis aims for validation of the modal calculations performed by the Semi-Analytical model for submerged gates, which include fluid structure interaction. Several experiments were executed in the wave flume at the faculty of Civil Engineering at the Technical University of Delft. Dry hammer tests, wet hammer tests and wave tests were executed for different water levels. Different plates were investigated in the experiments: Solid Plate and Reinforced Plate. A measurement plan was designed to obtain reliable results from the measurement devices (strain gauges and accelerometers). The experimental data was subjected to an Experimental Modal Analysis algorithm. The Frequency Domain Decomposition turned out to be most suitable for this situation. The mode shapes that were found were subjected to a Modal Assurance Criterion (MAC), in order to compare them with the semi-analytical prediction. The results from the wet modal analysis showed that the Solid Plate had good correspondence with the prediction of the semi-analytical model. The mode shapes turned out to have a high MAC values, while the natural frequencies showed small relative errors for the modes under consideration. The Reinforced Plate was less accurate. In the wave experiments the first three modes were found, which were also believed to have the highest energy input. Considerable high MAC values assured that the identified modes were indeed the same as the modes of the semi-analytical prediction. The natural frequencies showed larger errors for especially the first mode (approx. 30%). It was observed that several measurement errors might have influenced the results of the Reinforced Plate. After finalizing the experiments for this plate, I discovered that the stiffeners and front plates came loose from the U-frame. The dynamic quantities of the Reinforced Plate were therefore adjusted during the experiments. The datasets of the experiments that were most trustworthy were selected for the different analyses. The Regular Wave Impact experiments showed good correspondence and where therefore assumed to be correct. The Solid Plate was concluded to behave as predicted by the semi-analytical model. High correlation between the predicted and identified modes and small errors in the natural frequencies were observed. The data from the Reinforced Plate showed that the high energy modes were identified for the wave experiments. Modal shapes had high correlation between predicted and identified ones, while the natural frequencies had somewhat large errors. It was observed that small natural frequency errors for the input modes resulted in relatively small errors for the calculated modes. Further validation of the model should focus on the prediction of maxima and time series of the response. The step from modal analysis to a time series is a final step in the semi-analytical model.
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A new semi-analytical model is developed to predict the dynamic response of slender gates in combination with an overhang, which are subjected to standing waves. Still little is known for these types of gates for this specific forcing type. The semi-analytical model is still in its development phase and must be validated on its performance. This thesis aims for validation of the modal calculations performed by the Semi-Analytical model for submerged gates, which include fluid structure interaction. Several experiments were executed in the wave flume at the faculty of Civil Engineering at the Technical University of Delft. Dry hammer tests, wet hammer tests and wave tests were executed for different water levels. Different plates were investigated in the experiments: Solid Plate and Reinforced Plate. A measurement plan was designed to obtain reliable results from the measurement devices (strain gauges and accelerometers). The experimental data was subjected to an Experimental Modal Analysis algorithm. The Frequency Domain Decomposition turned out to be most suitable for this situation. The mode shapes that were found were subjected to a Modal Assurance Criterion (MAC), in order to compare them with the semi-analytical prediction. The results from the wet modal analysis showed that the Solid Plate had good correspondence with the prediction of the semi-analytical model. The mode shapes turned out to have a high MAC values, while the natural frequencies showed small relative errors for the modes under consideration. The Reinforced Plate was less accurate. In the wave experiments the first three modes were found, which were also believed to have the highest energy input. Considerable high MAC values assured that the identified modes were indeed the same as the modes of the semi-analytical prediction. The natural frequencies showed larger errors for especially the first mode (approx. 30%). It was observed that several measurement errors might have influenced the results of the Reinforced Plate. After finalizing the experiments for this plate, I discovered that the stiffeners and front plates came loose from the U-frame. The dynamic quantities of the Reinforced Plate were therefore adjusted during the experiments. The datasets of the experiments that were most trustworthy were selected for the different analyses. The Regular Wave Impact experiments showed good correspondence and where therefore assumed to be correct. The Solid Plate was concluded to behave as predicted by the semi-analytical model. High correlation between the predicted and identified modes and small errors in the natural frequencies were observed. The data from the Reinforced Plate showed that the high energy modes were identified for the wave experiments. Modal shapes had high correlation between predicted and identified ones, while the natural frequencies had somewhat large errors. It was observed that small natural frequency errors for the input modes resulted in relatively small errors for the calculated modes. Further validation of the model should focus on the prediction of maxima and time series of the response. The step from modal analysis to a time series is a final step in the semi-analytical model.
Vertical sliding valves that are part of a filling and emptying system of a lock are often subjected to an underflow of water during emptying and filling. The flow induces time varying forces on the structure which leads to dynamic behaviour of the valve. Whether the structure is in the range of resonance and what the amplitude of the vibrations will be depends on the mass, damping, stiffness and forcing quantities of the system. This thesis focussed on gaining insight in the behaviour of such a cylinder and its various components in terms of stiffness and damping of the total system including the vertical sliding valve. The research questions focussed on whether it is possible to influence the dynamic characteristics of a system (natural frequency and dynamic amplification) by adjusting the geometry of the hydraulic cylinder. Furthermore it is investigated which components are influencing the dynamic characteristics of the system and which damping and stiffness components are found to be subordinate to the dominant sources. Results were based on a Python script that included all relevant sources of damping and stiffness of a hydraulic cylinder, as well as the fluid structure interaction components such as added mass, damping and stiffness. The added damping components included the self-excitation suction damping. The sensitivity of different components to the natural frequency and dynamic amplification was explored. This was done for different cases, where in each case one variable varied while the others were kept constant. The results from the sensitivity analysis were used to find an optimal parameter that would lead to an optimal design in terms of natural frequency increase or decrease, reduction of the dynamic amplification and a minimal influence on the mass of the system. Besides these two studies, a third study was adopted to find the relative influence of different damping and stiffness components of the hydraulic cylinder for varying boundary conditions such as water level difference and gate opening. The study showed four components of a hydraulic cylinder that influenced the dynamic characteristics the most when varying their dimensions in a realistic range. These where the diameter of the hydraulic cylinder, the cylinder length, the thickness of the rod and the length of the tube that transport fluid into the cylinder. From these, the tube length and the cylinder diameters turned out to be the most effective design variables for tuning the stiffness, damping and correspondingly the natural frequency and the dynamic amplification of the system. Furthermore it was found that under all conditions (varying water level, gate opening height, pressure and stiffness), the stiffness was mostly determined by the axial stiffness of the rod and piston as well as the stiffness due to compaction of the cylinder fluid. For damping it was found that the cylinder only had limited influence and that most damping resulted from friction between the valve and the guiding rails.
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Vertical sliding valves that are part of a filling and emptying system of a lock are often subjected to an underflow of water during emptying and filling. The flow induces time varying forces on the structure which leads to dynamic behaviour of the valve. Whether the structure is in the range of resonance and what the amplitude of the vibrations will be depends on the mass, damping, stiffness and forcing quantities of the system. This thesis focussed on gaining insight in the behaviour of such a cylinder and its various components in terms of stiffness and damping of the total system including the vertical sliding valve. The research questions focussed on whether it is possible to influence the dynamic characteristics of a system (natural frequency and dynamic amplification) by adjusting the geometry of the hydraulic cylinder. Furthermore it is investigated which components are influencing the dynamic characteristics of the system and which damping and stiffness components are found to be subordinate to the dominant sources. Results were based on a Python script that included all relevant sources of damping and stiffness of a hydraulic cylinder, as well as the fluid structure interaction components such as added mass, damping and stiffness. The added damping components included the self-excitation suction damping. The sensitivity of different components to the natural frequency and dynamic amplification was explored. This was done for different cases, where in each case one variable varied while the others were kept constant. The results from the sensitivity analysis were used to find an optimal parameter that would lead to an optimal design in terms of natural frequency increase or decrease, reduction of the dynamic amplification and a minimal influence on the mass of the system. Besides these two studies, a third study was adopted to find the relative influence of different damping and stiffness components of the hydraulic cylinder for varying boundary conditions such as water level difference and gate opening. The study showed four components of a hydraulic cylinder that influenced the dynamic characteristics the most when varying their dimensions in a realistic range. These where the diameter of the hydraulic cylinder, the cylinder length, the thickness of the rod and the length of the tube that transport fluid into the cylinder. From these, the tube length and the cylinder diameters turned out to be the most effective design variables for tuning the stiffness, damping and correspondingly the natural frequency and the dynamic amplification of the system. Furthermore it was found that under all conditions (varying water level, gate opening height, pressure and stiffness), the stiffness was mostly determined by the axial stiffness of the rod and piston as well as the stiffness due to compaction of the cylinder fluid. For damping it was found that the cylinder only had limited influence and that most damping resulted from friction between the valve and the guiding rails.